OK when it comes to math I am not the sharpest knife in the draw by a long way, I have a problem an old fridge is measured as using
0.04 kwh per hour x 24 = .96
x 365 = 350.40

my electricity is 0.156 per kwh 350.40 x 0.156 = 54.6624 ….I know this 20 year old fridge is costing more than that per year can you see where I have gone wrong?

Well I can’t fault your maths. However, this excerpt from google may shed light on the situation:

A 1986-era 18 c.f. fridge uses 1400 kWh a year, while a modern energy-efficient model uses only 350 kWh — a whopping 75% reduction. At 15¢ kWh, trading in a pre-1986 fridge for a new efficient one would save about $158 a year in electricity costs. And some older fridges are even worse than the average.

How do you know it is costing more than that?

The 0.04/hr might also have been when it was new. You would have to measure it to check

And that’s before we even get into VA type stuff

Calculations are correct. Looking at newer models on ao.com they are showing as using between £35-45 a year.

If you asssume that it’s 40% less efficient though because of wear and tear on the colling system or the door seal not working properly it would still only be £76.52 a year.

Surely thats a false presumption that the fringe is exerting a constant draw

Power use will vary massively depending on how hard the compressor is working, which would be controlled by external factors such as external temperature, internal temperature setting and how often you open the door, even how full it is (I keep a load of bottles of water in as a cold sink).

I plugged a meter in to the socket and got the measurement 0.04 kwh.

I suspect the 40 watts you are quoting is simply incorrect. 40 watts is next to nothing in terms of power output. A fridge compressor typically consumes multiples of the quoted figure. So bearing in mind that the compressor runs only when the internal temperature gets above a pre determined level, an older (less efficient) fridge could be running a lot of the time attempting to reject heat into an already warm environment.

So more watts running for more time = higher bills.

Try plugging it into an plug that monitors energy usage.

D.

I found this calculator http://energyusecalculator.com/electricity_refrigerator.htm

but iam not sure what to put in the Watts section as I am measuring in KWH.

you are actually just measuring watts.

if your meter says its using 0.04 kilowatt hour / per hour then its using 0.04 Kilowatts or 40 watts.

Seems low though so double check you aren’t just getting a low figure when the fridge is effectively at idle

I plugged the meter in and ran it for 1 hour to get the reading of 0.04 kwh.

If it’s a cheap meter than it could be measuring VA rather than watts was so would over estimate. Any way, that was likely it just idling as others have said. You would need to do something like leave the door open for a bit then close it to make sure the motor was running. If you left it for an hour the meter may also not have been averaging correctly. It’s very difficult to know without knowing what the meter was

Ahh so if its 40 watts then i have the decimal point in the wrong place when doing my calculation for the 24 hour period giving me 960 not .96 yes ?

Nope decimal is in the right place. 40W = 0.04kW. What is likely to be wrong is value that you measured. Fridges earn their keep when being used, so door opening/closing, and room temperature (or higher) things being put in them.

Plug it in again, and leave it in for a week. See what you get then.

The online calculator would then bring back a horrendous figure of

Cost Per Hour:
0.1498
Cost Per Day:
3.5942
Cost Per Month:
109.34
Cost Per Year:
1312.04
kWh Per Day:
23.04
Hours Used Per Day:
24
Power Use (Watts):
960
Price (kWh):
0.156
Calculate Reset

40W for one hour is indeed 0.04kwh so you were correct

Wicki, as you’ll already know the fridge compressor doesn’t run all the time if it’s working properly. You would get a more accurate representation of power consumed by taking a longer average. This would help factor in environmental factors like opening and closing the door and ambient temps.

Ahh the thing is this old fridge is running nearly all the time i took a 2 hour measurement as well which confirms the result of just over 0.04 kwh.

Electricity is soo confusing.

A fridge compressor will use lots of power when starting up, but only for a very short amount of time (seconds or fractions of a second). Once it’s running then that power consumption drops right off.

Ok I’ll leave the meter on for 24 hours, bear in mind also the temp here has been hitting 37 and this fridge is like I said 20 plus years old And I can see daylight where the cooling pipe enters the box.

What meter is it? It might not be properly integrating/averaging

What’s the ventilation like at the rear of the fridge? If its congested back there and covered in a couple of decades of dust give it a bit of a vacuum. The coils at the back are trying to reject heat. If they’re insulated by dust you’re paying more because the compressor is having to work more often.

Its an unbranded cheapo I will admit but it measures the correct voltages according to my multi meter.

Yep, but the question really isn’t about voltage. It’s about how it measures current, power and how it averages it. E.g.. Does it add up the energy used and divide by time or does it just show a sort of rolling average over a few minutes

Hmmm all i know is it has a timer and counts the minutes hours and shows the kwh used.

How big is the fridge?

If the kwh keep going up then it might actually be ok. I would be tempted to check it by measuring something well known like a kettle for a minute. It should also go up while the kettle is on and then stay constant after

maybe 1.40 tall 600 wide

1kwh a day sounds about right to me for a fridge that old and that big

Fridges use electricity to move heat (they don’t make or absorb heat)

So the amount of electricity used depends on how much heat has to be moved, and how efficient the mechanism moving that heat is.

Fridges use a refrigerant, pumped by an electric pump. They try to keep the temperature in the fridge at a constant low temperature (say around 3 degC typically). When you put a new item in the fridge first that item must have heat removed from it’s mass (assuming it was hotter than the fridge temp when put in) and then all the fridge has to do is to take enough heat out of the cold box to compensate for the heat that leaks back in from outside (which of course depends how hot it is outside the fridge)

The reason new fridges are less costly to run than old ones is because they are better insulated, so less heat leaks back in and has to be taken back out again! Often old fridges are actually more efficient in terms of heat moved per unit of energy consumed because they use refrigerants that are more effective (but now have been banned for being really pretty nasty to the environment)

What this means is that the amount of energy your fridge uses over a short period may not reflect its average consumption over a year. Depending on how hot it is in your kitchen, when you last put a load of warm things in to cool down, when the door was last opened etc, short term measurements can be way too high, or way too low!

The final clever bit about fridges is they are more than 100% efficient in terms of the energy they required to move heat. Because they are not heat convertors, but just movers, they typically have an efficiency of around 200 to 300 percent. ie, 1 joule of electricity can move between 2 and 3 joules of heat!

The problem is I have 5 fridges and 3 are ancient they are sucking back the leccy I need to buy some new and rationalize down to 3

why so many? what do you use them for?

why so many? what do you use them for?

That deserves a thread all of its own. I’m guessing he’s a dealer in used body parts 😆

A small under counter in the kitchen because there is no room
another under counter in my old dads rooms
another in the cellar to suplement the small in the kitchen
and two freezers in the cellar as well.